(1) Field of the Invention
The present invention relates to a valve timing control apparatus for an internal combustion engine which is capable of variably controlling an open-and-closure timing of an engine valve which is an intake valve or an exhaust valve of the internal combustion engine in accordance with a driving condition of the engine.
(2) Description of Related Art
A generally available vane type valve timing control apparatus is structured for a vane member to be stable at a retardation angle side with respect to a timing sprocket caused by an alternating torque generated on a camshaft, in a state in which an operational force according to a hydraulic pressure is not generated in such a case of at a time of an engine stop.
However, in recent years, as disclosed in a previously proposed valve timing control apparatus, for example, as described in a Japanese Patent Application First Publication (tokkai) No. 2005-180378 published on Jul. 7, 2005 (which corresponds to a United States Patent Application Publication No. 2007/0095199 published on May 3, 2007), in a case where the operational force according to the hydraulic pressure is not generated, a spring force of a torsion spring causes a vane member to be mechanically stabilized toward an advance angle side or the operational force is assisted in the advance angle direction.
The torsion spring described in the above-described Japanese Patent Application First Publication No. 2005-180378 has one end bent toward an outside of a radial direction of the torsion spring and is fixedly retained in a retaining groove which is exclusively used for a retaining purpose and is installed on a housing and, on the other hand, has the other end bent toward an inside of the radial direction thereof and is fixedly retained into a retaining groove which is exclusively used for the retaining purpose and is installed on the vane member.